Can KTM build a significantly lighter 700-800cc twin? Is there a market for it?

Lot's of discussion about this topic in the 1190 thread already, so in order not to derail it any more I'm starting a new thread.

Many of the "old school" 950/990 owners are claiming that this would be a useless exercise as you would just give up a lot of horsepower for only a couple of lbs of weight loss.

Well, I don't agree.

The weight difference between a 690 and a 990 (non ABS!) is around 140 lbs, with the engines accounting for around 40 lbs of that. Considering the smaller displacement and that manufacturing technologies have improved, a die cast 700-800cc twin engine should be at least 10 lbs lighter than the 990, probably more.

So you've got around 110 lbs difference after the engine, you don't think you can beef up a 690 chassis enough to deal with 80-90 horses and add a fairing and be left over with a significant portion of that? The 450RR rear tank that bolts to the 690 chassis is available already and weighs maybe 1 lb more, and with it's 18 liters of fuel will give you better range than a 990 has.

And don't forget that the 690 already has 48mm forks, 21"/18" wheels with Dirt Star rims, the same brakes as the 950SE and that the 690 rally replicas and even the factory LC4 rally bikes (some sporting a >80HP 730cc engine) run through the desert at up to 200 km/h for two weeks during the Dakar using that same trellis frame and I have never heard of anybody having problems, have you?

I think with some modern and creative engineering a 80-90 HP 700-800cc twin with 360-380lbs (wet no fuel) is a realistic goal, and I'd buy one tomorrow.

Lot's of discussion about this topic in the 1190 thread already, so in order not to derail it any more I'm starting a new thread.

Many of the "old school" 950/990 owners are claiming that this would be a useless exercise as you would just give up a lot of horsepower for only a couple of lbs of weight loss.

Well, I don't agree.

The weight difference between a 690 and a 990 (non ABS!) is around 140 lbs, with the engines accounting for around 40 lbs of that. Considering the smaller displacement and that manufacturing technologies have improved, a die cast 700-800cc twin engine should be at least 10 lbs lighter than the 990, probably more.

So you've got around 110 lbs difference after the engine, you don't think you can beef up a 690 chassis enough to deal with 80-90 horses and add a fairing and be left over with a significant portion of that? The 450RR rear tank that bolts to the 690 chassis is available already and weighs maybe 1 lb more, and with it's 18 liters of fuel will give you better range than a 990 has.

And don't forget that the 690 already has 48mm forks, 21"/18" wheels with Dirt Star rims, the same brakes as the 950SE and that the 690 rally replicas and even the factory LC4 rally bikes (some sporting a >80HP 730cc engine) run through the desert at up to 200 km/h for two weeks during the Dakar using that same trellis frame and I have never heard of anybody having problems, have you?

I think with some modern and creative engineering a 80-90 HP 700-800cc twin with 360-380lbs (wet no fuel) is a realistic goal, and I'd buy one tomorrow.

What do you guys think?

the 690E has no sub frame, no provision for a luggage rack, not designed for 2 up and single front disc, no nav tower or wind protection.

All of those thing add weight and all of those things are things the market would want to make it compete with the other 800cc bikes... If you design it as a narrowly focused dirt adventure tourer and except people to travel lightly and are willing to trade ruggedness for weight I think it could be done and use more composite and TI construction it could be done.

If the 9x0 is so heavy where's the weight savings to be had? Short of a major cost increase to more exotic materials and AL frames

So, (maybe I am gallant with the lbs) it seems that a 185 kgs 700/800 twin is possible, fully fueled and with lower CG than the SE.

That's a good list.

I would also prefer a semi-dry sump engine to avoid the extra complexities during oil changes and the weight of an external tank etc.

For braking power I think the stock Brembo caliper with a single 320mm disc should be fine for most people, it will be better than the 950 SE and the F650GS twin with less weight and better clamping power. The limiting factor is the mostly the tire after all, this is why the single disc F650GS outbrakes the twin disc F800GS, both have the same Brembo calipers as 950/990. And if you really want to put on a sticky 19" or 17" tire then just upgrade to a Motomaster caliper and you will have all the braking power you could need, without the extra weight.

I would also prefer a semi-dry sump engine to avoid the extra complexities during oil changes and the weight of an external tank etc.

For braking power I think the stock Brembo caliper with a single 320mm disc should be fine for most people, it will be better than the 950 SE and the F650GS twin with less weight and better clamping power. The limiting factor is the mostly the tire after all, this is why the single disc F650GS outbrakes the twin disc F800GS, both have the same Brembo calipers as 950/990. And if you really want to put on a sticky 19" or 17" tire then just upgrade to a Motomaster caliper and you will have all the braking power you could need, without the extra weight.

If you want a really small light motor with great ground clearance where is the sump going to be? And how much oil is it going to hold? I'd rather not have a 1qt motor like an RFS for a adv bike... Nor would I want to worry about if the motor is running low on oil loosing oil pressure.

The 320mm disc is allot more likely to be damaged. The rotor is weaker side to side and lower making it more likely to get it by a rock or catch the ground in a crash... With a dual disc setup you also have redundancy in the system in the event you damage one rotor you can covert it to a single disc.

Not to mention it's not just about brake power, but about thermal efficiency over repeated stops...

The 320mm disc is allot more likely to be damaged. The rotor is weaker side to side and lower making it more likely to get it by a rock or catch the ground in a crash... With a dual disc setup you also have redundancy in the system in the event you damage one rotor you can covert it to a single disc.

Not to mention it's not just about brake power, but about thermal efficiency over repeated stops...

Have you actually tried a single disc setup or is this all theoretical?

I can (and do) live with the additional risk that a 0.4" lower rotor brings, not an issue in real life IME.

I don't think I have ever read of a single person unbolting their second disc because it was damaged but you are free to carry a spare if you feel that's necessary, it will still weigh less since there is no second caliper.

With a 21" wheel and a TKC type tire even repeated stops are not going to overheat a single disc. And again, if you want to use it primarily on tarmac - presumable with a stickier tire - then the Motomaster caliper is very simple upgrade. Those hold up even on the race track in the heavier and more powerful 990 as some other inmates have tested.